1 20 HAIRS. [sect. 66. 



What has been said applies only to the eyelashes. The hair- 

 follicles of the head, and of the other parts of the body of the 

 child above-mentioned, contained each only one hair ; but this, 

 presented at its bulb, a process which, though unaccompanied by 

 a new hair, exactly resembled that which precedes the shedding of 

 the eyelashes. These processes are, in general, very common in 

 the hairs of children in the first year after birth. I believe I am 

 not wrong, when from the presence of these processes I infer the 

 occurrence of a general shedding of the hair ; and especially since 

 it is certain, that, in many children, the hairs of the head fall 

 out in from two to six months after birth, and are replaced by 

 new ones. Nevertheless, further observations will be necessary to 

 decide in what period of time this first change of the hair takes 

 place, in what hairs it occurs, and whether repetitions of the 

 process may not perhaps take place at a later period. 



In the periodical shedding of the hair of animals the new hairs are likewise 

 formed in the follicles of the old ones, as the observations of Heusinger and 

 Koldrausch. and recently also those of Zanger, Gegenbaur, and Steinlin show; 

 still, according to the last author, with whom, however, Laager does not 

 entirely agree, the steps of the process do not appear to be exactly the same 

 as in man. 



§ 66. Physiological Remarks. — The hairs possess a determinate 

 length, according to their situation and the sex of the individual, 

 but grow again when cut, and thus agree with the other horny 

 structures. The place whence the growth of hair proceeds is, 

 undoubtedly, the bottom of the hair- follicle. Here new elements 

 are developed around the hair-papilla — through means of a blastema 

 exuded from its vessels, or those of the hair-follicle itself — by the 

 continual multiplication of the cells there situated, while the 

 elements already formed, and now somewhat higher placed, are 

 transformed, uninterruptedly, the middle ones into the cells of the 

 medulla, those immediately following into the plates of the fibrous 

 substance, and the outermost into epidermic scales ; and thus the 

 cornified part of the hair is continually pushed from below 

 upwards, and elongated. In the latter no formation of elementary 

 parts occurs, at most only a certain alteration of those already 

 existing, which causes a gradual thinning of the root from the 

 bulb upwards, until it is reduced to the thickness of the shaft. 

 Higher up even these changes of the elementary parts are wanting ; 

 consequently hairs, when cut, do not acquire new points. The 

 root-sheaths and the outer layer of the hair-cuticle do not take 

 part in the growth of cut hairs. 



